Powders of silica-oxide and mixed silica-oxide and method of preparing same

ABSTRACT

Silica powders and mixed silica-oxide powders and methods of preparing such powders for use as catalyst supports for polymerization processes.

FIELD OF THE INVENTION

[0001] This invention relates to silica powders and mixed silica-oxidepowders and methods of preparing such powders for use as catalystsupports for polymerization processes.

BACKGROUND OF THE INVENTION

[0002] The use of amorphous gels and precipitates as support materialfor polymerization catalysts is known. For example, aluminophosphategels and precipitates have often been used for such support materials.In some cases, the support was improved by incorporating silica into thealuminum phosphate support.

[0003] While aluminophosphates have long been known, along with theirmethods of preparation, such aluminophosphates have not as yet achievedcommercial success. Part of this is believed to be that the prior artaluminophosphates lacked a combination of physical properties which havebeen found to characterize superior polymerization catalysts. It is thecombination of a high macropore volume of at least 0.1 cc's per gramplus a fragmentation potential (to be defined below) of preferably 30 to60 plus a preferred mesopore volume of 0.3 to 0.8 cc's per gram whichparticularly characterize the superior polymerization catalysts. In twoprior inventions of Applicants (Pecoraro and Chan, U.S. patentapplication Ser. No. 08/742,794; Auburn and Pecoraro, U.S. patentapplication Ser. No. 08/741,595), which are incorporated herein byreference, a new aluminophosphate with both high macropore volume and afragmentation potential about 30 was developed which was also bothphysically and thermally stable. It is believed that the presence ofsheets of aluminophosphate in the microstructure results in the packingof the microstructures in such a way that a high macropore volume and ahigh fragmentation potential are achieved along with physical andthermal stability.

[0004] In another related invention by Applicants (U.S. application Ser.No. 08/961,825, Auburn, Pecoraro and Chan), which is acontinuation-in-part of 08/741,595 and 08/742,794 discussed above, andwhich is also incorporated by reference herein, a silica-modified,amorphous aluminophosphate composition which like the previousinventions exhibits a microstructure of sheets and exhibits spheres ofsilica-modified aluminophosphate as well.

[0005] The use of silica alone or the combination of silica with otheroxides such as alumina or titania or vanadia to form such amorphouscompositions for use as polymerization catalyst support material is alsoknown. Previously, the microstructure of such supports primarilycontained small particles. As a result of this small particle structure,it was difficult to tailor the materials over a wide range of poresizes, distributions and volumes, and of acceptable fragmentationcharacteristics.

[0006] It would be desirable to find silica support materials whichcould be used over a wide range of pore sizes, distributions and volumesand of acceptable fragmentation characteristics.

[0007] The present invention has achieved such materials. The presentinvention has achieved high surface area, amorphous silicas whichsurprisingly form a continuous network matrix, rather than the typicalsmall particles found in conventional amorphous silicas. Furthermore,the pore size and the distribution and volume of the pore size can betailored over a wide range. Surprisingly, also, the present inventionachieves an amorphous SiO₂ base composition with a non-particulate,dense, network matrix and encapsulated less dense, non particulateregions with true macropores. In one embodiment, the present inventionalso comprises a sheet-like microstructure.

SUMMARY OF THE INVENTION

[0008] One object of the present invention is to provide an amorphousSiO₂ or mixed oxide silica base composition comprising:

[0009] (a) a non-particulate, dense, continuous network matrix; and

[0010] (b) encapsulated, less dense, non particulate regions with truemacropores.

[0011] Another object of the present invention is to provide such anamorphous SiO₂ or mixed oxide silica base composition in which the gelmatrix further comprises a sheetlike microstructure.

[0012] Still another object of the present invention is to provide suchan amorphous SiO₂ or mixed oxide silica base composition in which thecomposition has surface areas in a range of from 150 to 600 m²/gm.

[0013] Yet another object of the present invention is to provide such anamorphous SiO₂ or mixed oxide silica base composition in which thecomposition has a mean mesopore diameter in a range of from 60 to about250 Å.

[0014] An additional object of the present invention is to provide suchan amorphous SiO₂ or mixed oxide silica base composition in which thecomposition has a measured pore volume in a range of from about 0.5 to1.5 cc/gm.

[0015] Still another object of the present invention is to provide suchan amorphous SiO₂ or mixed oxide silica base composition in which thecomposition has a macropore volume of at most 0.5 cc/gm.

[0016] Yet another object of the present invention is to provide anamorphous mixed oxide silica base composition selected from the groupconsisting of silica alumina, silica titania, silica vanadia and silicazirconia.

[0017] An additional object of the present invention is to providepowders produced from such an amorphous SiO₂ or mixed oxide silica basecomposition.

[0018] A further object of the present invention is to provide suchpowders which are spray dried.

[0019] Yet a further object of the present invention is to provide suchpowders which are vacuum dried.

[0020] Still a further object of the present invention is to providesuch spray dried powders having fragmentation potentials in a range offrom about 20 to about 30.

[0021] Another object of the present invention is to provide a catalystcomprising such a SiO₂ base composition, the composition beingimpregnated with a catalytic amount of at least one transitionmetal-containing compound.

[0022] Yet another object of the present invention is to provide such acatalyst in which the at least one transition metal-containing compoundis a chromium compound.

[0023] Still another object of the present invention is to provide sucha catalyst in which the at least one transition metal-containingcompound is present in an amount of 0.1 weight percent or greater basedon the total catalyst weight.

[0024] An additional object of the present invention is to provide sucha catalyst in which the at least one transition metal-containingcompound is present in an amount in the range of from about 0.1 weightpercent to about 10 weight percent.

[0025] Yet an additional object of the present invention is to provide apolymerization process comprising contacting such a catalyst with atleast one alpha-olefin under polymerization conditions.

[0026] Still an additional object of the present invention is to providea method for preparing a silica gel composition which is a precursormaterial for a silica powder material with a microstructure comprising anon-particulate, dense, continuous network matrix and encapsulated, lessdense, non particulate regions with true macropores, the methodcomprising:

[0027] (a) forming a first aqueous solution comprising silica ions;

[0028] (b) forming a second aqueous solution capable of neutralizingsaid first aqueous solution; and

[0029] (c) contacting said first and second aqueous solutions in amixer-reactor under mixing conditions to form the silica gelcomposition.

[0030] An additional object of the present invention is to provide anolefin polymerization catalyst prepared from a silica gel compositionobtained by such a method.

[0031] Yet another object of the present invention is to provide such amethod in which the first aqueous solution is an acidic solutioncomprising sodium silicate and acid and in which the second aqueoussolution has a pH above 8.

[0032] Still an object of the present invention is to provide such amethod in which the second aqueous solution is an ammonia based materialselected from the group consisting of ammonium hydroxide; ammoniumcarbonate; ammonium bicarbonate and urea.

[0033] An additional object of the present invention is to provide sucha method in which the first aqueous solution is a basic solution ofsodium silicate and in which the second aqueous solution has a pH below6.

[0034] Yet an additional object of the present invention is to providesuch a method in which the second aqueous solution is sulfuric acid.

[0035] Still an additional object of the present invention is to providesuch a method, in which the apparent average shear rate in themixer-reactor is greater than about 0.5×10⁴ sec⁻¹.

[0036] Another object of the present invention is to provide such amethod in which the neutralization step is conducted in such a mannerthat the pH of the combined first aqueous solution and the neutralizingmedium is controlled in the range of about 3.5 to about 11.

[0037] Yet another object of the present invention is to provide such amethod in which the catalyst is activated by being heated to atemperature in the range of 300° C. to 900° C. for from 2 to 16 hours.

[0038] Still another object of the present invention is to provide sucha method further comprising the steps of:

[0039] (a) preparing an aqueous slurry of amorphous silica gel bycontinuously feeding an acidic solution comprising sodium silicate andacid to an emulsifier mixer while simultaneously and continuouslyfeeding to said mixer an alkaline solution;

[0040] (b) operating said mixer with sufficient shear so that theprecipitated silicate has sheets of silica in its microstructure;

[0041] (c) recovering said silica from said aqueous slurry using avibrating filtration membrane to a solids content from 8 to 20 wt. %,after washing;

[0042] (d) drying and calcining the silica from (c);

[0043] (e) dispensing a chromium compound substantially uniformly ontosaid silica to form a catalyst having from 0.01 to 4 wt. % chromium;

[0044] (f) drying said catalyst; and

[0045] (g) activating said dry catalyst from (f) by heating to atemperature from 300° C. to 900° C. for from 2 to 16 hours.

[0046] Yet another object of the present invention is to provide anolefin polymerization catalyst prepared by such a method.

[0047] Another object of the invention is to provide such a methodfurther comprising aging the silica gel composition in deionized waterfor up to one hour.

[0048] Yet another object of the present invention is to provide amethod of preparing the silica powder composition from such a silica gelcomposition comprising the steps of:

[0049] (a) washing the silica gel with solutions of ammonium acetate,bicarbonate or nitrate;

[0050] (b) washing the silica gel composition in deionized water tofurther replace salts-contaminated water in the composition with freshwater; and

[0051] (c) drying the washed composition to remove substantially allwater.

[0052] Still another object of the present invention is to provide sucha method further comprising calcining the dried composition in a fixedfluid bed type calciner for up to 8 hours at a maximum temperature of450° C.

[0053] Another object of the present invention is to provide apolymerization process comprising contacting at least one mono-1-olefinhaving from 2 to 8 carbon atoms per molecule under polymerizationreaction conditions in a polymerization reaction zone with a catalystcomprising an active catalytic component on a silica support comprising(a) a non-particulate, dense, gel matrix; and (b) encapsulated regionswith true macropores.

[0054] Still another object of the present invention is to provide sucha polymerization process in which the catalytic component comprises achromium component on the silica support.

[0055] Yet another object of the present invention is to provide such apolymerization process in which the at least one mono-1-olefin isselected from ethylene; propylene; butene-1; hexene-1 and octene-1.

[0056] An additional object of the present invention is to provide sucha polymerization process in which the at least one mono-1-olefincomprises ethylene and from 0.5 to 2 mole percent of one additionalmono-1-olefin selected from propylene; butene-1, hexene-1 and octene-1.

[0057] A further object of the present invention is to provide a methodfor preparing silica alumina powder material with a microstructurecomprising a non-particulate, dense, continuous network matrix andencapsulated regions with true macropores and sheets, the methodcomprising:

[0058] (a) preparing an acid aqueous solution comprising aluminum andsilicon ions;

[0059] (b) preparing a basic aqueous solution comprising ammoniumhydroxide;

[0060] (c) mixing the acidic aqueous solution and the basic aqueoussolution in a mixer to obtain a gel slurry with a microstructurecomprising a non-particulate, dense, continuous network matrix,encapsulated regions with true macropores and sheets;

[0061] (d) maintaining the gel at approximately pH 8.0 for up to onehour before washing the gel slurry;

[0062] (e) washing the gel slurry first with an aqueous ammonium acetateor ammonium bicarbonate solution, then with water to obtain a gelconductivity below 1,000 mmhos;

[0063] (f) acidifying and concentrating the gel slurry by adding acid tothe gel slurry to achieve a pH below 6.0 while gradually removing waterfrom the gel slurry; and

[0064] (g) drying and calcining the gel slurry to form thesilica-alumina powder material.

DESCRIPTION OF THE DRAWINGS

[0065] FIG. 1 is a side view of a mixer-reactor.

[0066] FIG. 2 is a top view of a mixer reactor.

[0067] FIG. 3 is a TEM Photomicrograph of Example Sample C1936-20-13 (EM2829) taken at magnification 30 KX. It shows the particulate nature ofthe sample.

[0068] FIG. 4 is a TEM Photomicrograph of Example Sample EP-50 (EM 3309)taken at magnification 50 KX. It shows the gel network and small TiO₂particles.

[0069] FIG. 5 is a TEM Photomicrograph of Example Sample C1935-23B (EM3821) taken at magnification 5 KX. It shows pockets and sheets.

[0070] FIG. 6 is a TEM Photomicrograph of Example Sample C1935-44B (EM3735) taken at magnification 50 KX. It shows the pore size in thematrix.

[0071] FIG. 7 is a TEM Photomicrograph of Example Sample C1935-47B (EM3728) taken at magnification 50 KX. It shows the pore size in the matrixgetting bigger than in FIG. 6.

[0072] FIG. 8 is a TEM Photomicrograph of Example Sample C1935-48B (EM3743) taken at magnification 50 KX. It shows the pore size in the matrixgetting even bigger than in FIG. 7.

[0073] FIG. 9 is a TEM Photomicrograph of Example Sample C1252-36B (EM0331) taken at magnification 10 KX. It shows the pore matrix withoutsheets.

[0074] FIG. 10 is a TEM Photomicrograph of Example Sample C1934-45 (EM2269) taken at magnification 10 KX. It shows the dense matrix with manysheets.

DETAILED DESCRIPTION OF THE INVENTION

[0075] The present invention relates to high surface area, amorphoussilicas which form a continuous network matrix, rather than the typicalsmall particles found in conventional amorphous silicas. Furthermore,the pore size and the distribution and volume of the pore size can betailored over a wide range so that the silicas have uniquemicrostructures and varied physical properties, such as surface area,pore volume, mean mesopore size, mesopore size distribution, macroporevolume and acceptable fragmentation potentials and methods of makingsuch silicas.

[0076] An especially significant aspect of the present invention is theachievement of “true” macropores in the amorphous silica material. Thesemacropores are “true” in the sense that their existence is verified andtheir structure observed and measured by TEM techniques, differing from“apparent” macropores which are observed and measured by mercuryporosimetry.

[0077] Mercury porosimetry is the common technique for measuring theamount of macropores in a catalyst sample. The technique involvessubjecting the sample which was immersed in Hg to increasing pressure.The pressure change starts from atmospheric (14 psi) to about 60,000psi. The volume change in the Hg level is monitored and plotted againstthe pressure change. The change in Hg level was assumed to be the resultof the Hg penetrated into the pore spaces of the catalyst. The plot ofthe Hg volume change against the applied pressure can then be presentedas the pore size distribution of the catalyst.

[0078] However, when the skeletal framework structure of the catalystdeparts significantly from being infinitely rigid, some of the volumechange in Hg level recorded by the instrument comes about because theporous catalyst particle was compressed or “squeezed” and not Hgpenetrated into the pores. Hence, the instrument could report theexistence of macropores while in reality there were none present,especially in the case of silica based catalysts. A detailed discussionof this phenomenon has been published by Vittoratos and Auburn. (E. S.Vittoratos and P. R. Auburn; “Mercury Porosimetry Compacts SiO₂Polymerization Catalysts”, J. of Catalysis, 152, 415-418 (1995)). TEM isthe only technique to verify the existence of true macropores. However,the usefulness of TEM to quantify the amount of macropores is at bestquite limited, because of the difficulty of visually identifying andcounting each macropore in a TEM micrograph.

[0079] It is thus clear that the mercury porosimetry instrumentpractically always overestimates the amount of macropores. The truevalue matches the apparent (reported) value only for the limiting caseof an infinitely rigid sample. The apparent value can be positive evenwhen the true value (verified by TEM) is zero. EP-50 is an example of acommercially available silica material which has been tested with themercury porosimetry method and apparent macropores were found but werenot verified by the TEM method.

[0080] The invention also relates to mixed silica-oxides in which theoxide is alumina, titania, zirconia, vanadia, etc., and combinationsthereof, with unique microstructures, unique catalytic performance andvaried physical properties and methods of making such materials. Suchmixed silica-oxides also have continuous, tightly packed, gel networkwhich routinely contain the unique sheet structures. Furthermore, themixed oxides are homogeneous (i.e., no individual separate oxide phasesare observed), and the pore size, pore size distribution, and volume(meso) of these materials can be tailored also.

[0081] These silicas and mixed-oxide silicas are prepared via gelationof sodium silicate alone or in combination with the precursors of theother oxides. The gelation can proceed from either the acid or the baseside. but it must be done with a high rate of mixing with shear forces.The gel slurry can be washed at different pH's via a batch or via aV*Sep process to remove contaminant salts and to dewater the gel slurry.The washed gels may be aged at various pH's, temperatures and times toalter the meso and macropore characteristics. Spray drying is thepreferred method of forming and drying.

[0082] There are, of course, various types of mixing techniques andapparatus which generate varying levels of shear delivery mixing. Seefor example, “Scaleup and Design of Industrial Mixing Processes” by GaryB. Tatterson, McGraw-Hill, Inc. (1994) and especially FIG. 2.9 whichillustrates the shear level of various types of mixers and impellers.Referring to FIG. 2.9 of Tatterson, which is incorporated herein byreference, the colloid mills, saw blade type impellers; homogenizers andstator rotor mixers provide the highest level of shear while thehydrofoil and propeller provide the lowest shear. The newer jet streammixers can also be employed with sufficient shear as taught herein.

[0083] Shear in this specification means shear rate which is a change invelocity (ΔV) divided by a change in distance (Δd). For example, in arotor shear mixer, the fluids to be mixed usually are pumped into therotor stator chamber through concentric tubes. The rotor stator chamberconsists of a rotor revolving at some desired rate and a “stator” orsurrounding wall close to the tips of the revolving rotor. The wall isprovided with openings to permit the mixed fluids to be removed orwithdrawn quickly and continuously from the rotor-stator chamber.

[0084] Using the rotor stator mixer as an example, the velocity of thefluid is highest at the tip of the rotor impeller and is zero at thewall. Thus, the ΔV is taken as the velocity at the tip which can becalculated by multiplying the revolutions of the rotor per second timesthe radius of the rotor, i.e.:

ΔV=ND/2

[0085] where N=revolution of the rotor per second; D=diameter of rotor.

[0086] The “change in distance”, Δd, is equivalent to the distance overwhich one measures the change in velocity over the change in distanceand is calculated by the equation: $\begin{matrix}{{Apparent}\quad {Average}} \\{{{Shear}\quad {Rate}}\quad}\end{matrix} = \frac{\Pi \quad {ND}}{W}$ Π = pi = 3.1416

π=pi=3.1416

[0087] where

[0088] N is the revolutions of the impeller per second;

[0089] W is the distance between the tip of the impeller and the wall ofthe mixer; and

[0090] D is the diamieter of the rotor (in the case of rotor-statormixer) or can be the thickness of the impeller blade for other mixers.

[0091] It will be obvious to those with ordinary skill in the art thatshear rates can be increased by increasing ΔV or decreasing Δd.

Gelling Silica Salts

[0092] It is possible to form gel from silica salts by either adding anacid such as sulfuric acid to sodium silicate or adding a base such asammonium hydroxide (sodium silicate plus acid). It is also possible toform gels from an acidic mixture of oxide precursors and a sodiumsilicate plus acid by adding a base such as ammonium hydroxide. In apreferred embodiment of making silica, adding acid to sodium silicatesolutions was used. The acid and base solutions were mixed withhigh-shear, continuous gelation (CHSG) using a two-stream feed systempumped directly into a Ross mixer (reactor). For gelling to occur in thehigh shear reactor, it was necessary to determine the acceptableconcentrations of the reacting silica salt, the pH, the temperature, themixing rate, and the stator configuration. Removing the residual saltsis important.

[0093] Achieving the right degree of washing with a batch (i.e.,repulping and filtering) or a continuous (i.e., V*Sep difiltration)process has a significant effect on both the performance of the finishedcatalyst and the outcome of any subsequent aging steps. The amount ofresidual salt influences the type and degree of aggregation of theprimary particles subsequently affecting the pore size and pore sizedistribution of the dried powder. In addition, an aging step definitelycan be used to vary physical properties of resultant SiO₂ bases.

Preparation of SiO₂ Powders “General Procedure” Step 1—Preparation ofSolution of Silicate Anions

[0094] (A) Add the desired amount of sodium silicate to DI water withmixing.

[0095] (B) Dilute the sulfuric acid with DI water by weight.

Step 2—Gelation

[0096] The silicate solution formed in Step 1 and sulfuric acid solutionwere simultaneously pumped into the mixing chamber of a Ross-In-LineLaboratory Emulsifier (obtained from Charles Ross and Son Company,Hauppauge, N.Y., Model ME 300L) shown diagramatically in FIG. 1(sideview) and FIG. 2 (topview). Referring to FIGS. 1 and 2, the basicsolution silicate anions prepared in Step 1A is pumped into the mixingchamber 10 through the outer ¼″ inside diameter tube 12 and the sulfuricacid prepared in Step 1 B is pumped into mixing chamber 10 through theinner, ⅛″ inside diameter, tube 14. The mixing chamber 10 is fitted witha rotor impeller 16 having four arms and a stationary cylindrical wall18 surrounding the rotor impeller 16 and in relatively close proximityto the tips of the impeller arms. The stationary wall 18 is providedwith slots 20 through which the fluids and produced hydrogel pass intothe annular portions 22 of mixing chamber 10 and then out of the mixingchamber 10 through outer housing 24 and line 26. The acid and basesolutions react in the mixing chamber 10 while the rotor impeller 16operates at the desired revolutions per minute to provide the apparentaverage shear rate as taught above. The distance between the tip of onearm of impeller 16 and wall 18 is the “W” for use in the shear rateequation set forth earlier in this specification. The specific “W” forthe mixer-reactor used in the working examples below was 0.01 inches andthe diameter “D” of the rotor was 1.355 inches. The rate of addition ofthe acid and base solutions into the mixing chamber 10 is set to achievedesired pH at the outlet 24.

Step 3—Washing

[0097] The hydrogel was washed either by a batch process or bydiafiltration. In one case, Examples 14 and 15, the same hydrogel waswashed both ways.

Batch Washing

[0098] The hydrogel was blended with the desired wash solution in aWaring blender, mixed for about 15 minutes with a marine impellar mixer,and then filtered. This was done until the conductivity of the filtrateequaled the conductivity of the wash solution. Then the hydrogel wasblended with DI water and filtered to yield a gel cake.

Diafiltration

[0099] The hydrogel in the holding tank was diluted with hot (50° C.) DIwater to about 4 to 10 weight percent solids as measured by an LOMinstrument (CEM AVC 80).

[0100] This dilute hydrogel was washed on a vibrating filtrationmembrane machine (New Logic International V*SEP machine (Series P) whereV*SEP stands for Vibratory Shear Enhanced Processing). This washingprocess known as difiltration involves dewatering the hydrogel andadding fresh DI water at the same rate at which the filtrate or permeatecontaining the contaminated salts is removed. The washing is continueduntil the desired conductivity of the permeate as measured by aconductivity meter (Yokogama Model SC400 conductivity converter) isachieved.

[0101] Once the desired conductivity was achieved, the hydrogel solutionwas concentrated to the maximum “pumpable” weight percent solids (byLOM).

[0102] This was done by dewatering the hydrogel solution by not addingfresh DI water.

Step 4—Aging

[0103] The washed hydrogel was filtered to yield a filter cake. Thefilter cake was diluted with DI water to allow for mixing with a marineimpellar mixer. The pH of the slurry was adjusted with either aceticacid to a pH equal to about 5.6 or with ammonium hydroxide to a pH equalto about 9.6. The pH adjusted slurry was heated to 50° C. over about 15minutes and then held at 50° C. for about 15 minutes. The hot agedslurry was then pumped to the feed system of the spray dryer.

Step 5—Drying Vacuum Drying

[0104] The gel cake was dried in a vacuum oven at 80° C. overnight.

Spray Drying

[0105] The hydrogel from Step 3 or 4 was pumped to the feed system of aStork Bowen BE 1235 spray dryer and dried. The spray dryer conditionswere varied, by means well known to those having ordinary skill in theart, to achieve a desired particle size, LOM moisture weight percent andother desired characteristics.

Step 6—Calcination

[0106] The spray dried from Step 5 was calcined in a muffle furnace forone hour at 400° C.

[0107] The vacuum dried hydrogel was calcined in a muffle furnace forone hour at 400° C.

[0108] In some Examples below, the uncalcined (as vacuum dried or spraydried) silica was impregnated with a chromium salt to deposit about 1weight percent chromium on the support on an LOI basis, done at 1000° F.for one hour. Chromium impregnation is done using a Buchi rotovap. Amaximum of 50 g of powder is added to a 500 ml rotovap flask. About 75to 100 g of the solvent methanol or DI water is added to the powder(solvent to powder ratio is always approximately 2 to 1 by weight).Swirl the flask to achieve uniform wetting of the powder. Weigh thechromium (III) acetate hydroxide and dissolve in the solvent(approximately 15-30 ml). Add the chromium solution to the powder slurryand swirl to evenly coat the powder. Attach flask to the Buchi and spinthe flask for approximately 5 minutes without vacuum to mix the slurry.Using a vacuum regulator and vacuum pump, set the vacuum toapproximately 200 to 400 mm Hg, and lower the flask into an 80° C. waterbath when water is the solvent or a 40° C. water bath when methanol wasthe solvent. Maintain these conditions until approximately 80% of thesolvent was evaporated. Slowly increase the vacuum to approximately 600mm Hg as necessary to remove the last of the solvent without “bumping”any of the slurry/powder over. When the powder appears completely dry,increase the vacuum to maximum for approximately 5 minutes. After thelast vacuum adjustment is complete, release the vacuum and shut off theBuchi.

[0109] Such silicas and mixed silica-oxides have a wide variety of uses,especially as supports for ethylene polymerization. Also, because of thecatalytic and physical properties, the mixed silica-oxides can betailored for use as FCC catalysts or for use in hydroprocessing such ashydrodenitrification, hydrodesulfurization, hydrodewaxing, hydrocrackingor hydrogenation.

[0110] The physical properties such as surface area and pore size andpore size distribution can differ significantly not only betweenhydrogels and precipitates of silicas and mixed oxide silicas, but evenbetween various types of precipitates depending on the treatment of theprecipitates both during and after preparation, i.e., hot washing; hotaging, etc.

[0111] Certain silica and mixed oxide silica precipitates have now beendiscovered which have excellent thermal and physical stability, togetherwith a relatively high amount of macroporosity so that these materialsare particularly suited for use as catalyst support materials,especially for use in reactions involving relatively large molecules(e.g., residua) in order to allow the molecules easy ingress and egress.

[0112] The silica and mixed oxide silicas are characterized by beingamorphous; having a non-particulate, dense, continuous network matrix,and having encapsulated regions with true macropores. Some of the silicaand the silica-alumina precipitates have also been found to havesheet-like microstructures.

[0113] The new silicas and mixed oxide silicas have, in addition,certain characteristics in their preferred form as set forth below.These characteristics were determined after drying and calcining thesilicas at 400° C. for 1 hour and mixed oxide silicas, i.e.,silica-aluminas, at 593° C. for 2 hours.

[0114] (1) Surface area by the BET Method

[0115] Typically, the surface area of the new silicas and mixed oxidesilicas is from about 150 to 600 m²/gm.

[0116] (2) Macropore Volume by the Mercury Technique

[0117] By “macropore volume” in this specification is meant the volumeoccupied by pore sizes in excess of 1000 Å. It is particularly desirablefor some end uses such as the polymerization of olefins to have amacropore volume in excess of 0.1 cc's per gram. The problem in the pastwas obtaining supports with a “true” macropore volume in excess of 0.1cc's per gram along with physical stability. The silicas and mixed oxidesilicas of this invention have a high macropore volume and arephysically stable as shown by the fact they were successfully used in afluid bed gas phase polymerization of ethylene.

[0118] The macropore volume is taken by the mercury porosimetry test (byASTM Designation: D4284-88 where gamma is taken to be 473 dynes per cmand the contact angle is taken to be 140 degrees).

[0119] The macropore volumes of the new silicas and mixed oxide silicasare at most 0.5 cc's per gram.

[0120] (3) Mean Mesopore Diameter by the BET Method

[0121] The mean mesopore diameter of the silicas and mixed oxide silicascan be from 60 to about 250 Å.

[0122] (4) Fragmentation Potential and Sonication Number

[0123] The testing of catalysts so as to determine attritioncharacteristics is recognized in the art. These tests typically involveintroduction of catalyst particles into a vessel and subsequentagitation of the particles. In such an arrangement, attrition resultsprimarily from abrasion caused by particles impacting with each other aswell as with the wall of the vessel.

[0124] For example, in processes where particles are subjected tofluidized bed conditions, fluidized tests such as air-jet testing arecommon in as far as they can be considered directly relevant to theperformance of particles under such conditions.

[0125] While such tests can be effective in testing attrition undercertain conditions, they have largely proven ineffective with respect topredicting the effectiveness of catalysts in processes where theattrition is related to the fractionation of the catalyst.

[0126] Moreover, such techniques fail to accurately report thatpolymerization catalysts, unlike catalysts employed in other processes,e.g., catalytic cracking, are subject to attrition at two differentstages, i.e., activation and polymerization. Thus, while traditionaltechniques, e.g., air-jet testing, may provide an effective model forattrition occurring during activation, such techniques are not aneffective model for attrition occurring during polymerization and thusare not sufficient to deal with such catalysts.

[0127] One particular process in which fractionation of the catalystoccurs is the polymerization of olefins. Olefin polymerization processesare well recognized in the art. Typical examples of such processesinclude slurry batch, e.g., slurry loop and gas phase olefinpolymerization processes.

[0128] Although each of these processes utilize catalysts in theproduction of polyolefins such as polyethylene, they differsignificantly with respect to the dynamics of particle growth therein.For example, gas phase processes include as much as 85% ethylene whileslurry loop type processes have a much lower ethylene solubility, e.g.,typically 8% maximum. Accordingly, catalysts which may be effective inone olefin polymerization process may not be found effective in anotherprocess. The new silica supported polymer catalysts of this inventionare effective in batch polymerization processes. One aspect of thepresent invention is based upon the surprising discovery that the“fragmentation potential” of catalysts, such as olefin polymerizationcatalysts, as determined by sonication, can be used in determining theexpected efficiency of a catalyst in a process where fragmentation willoccur.

[0129] The sonication process for use in the present invention caneffectively be employed within any sonication environment withsonication baths, and in particular sonication baths employing water,being preferred.

[0130] This sonication test can then typically take on one of two forms.The material can be sonicated for a predetermined period of time, e.g.,30 minutes, and the increase in fines, e.g., percent increase,subsequent to sonication can be determined. This test directly provideswhat is called the “fragmentation potential”.

[0131] Alternatively, the material can be sonicated for a period of timesufficient to reach a preselected mean particle size. The result of thisparticular test is called the “Sonication Number”. Although thisspecification will typically make reference to the fragmentationpotential, the concepts and advantages are the same for both of thesebasic tests.

[0132] In fact, as is readily apparent, these tests are basicallyanalogous with the numerical results being inversely related. That is, acatalyst which has a small increase in fine production over apredetermined period of time will typically require a longer time toreach the preselected mean particle size. The inverse is also true; acatalyst having large percent increase in fine production will have asmaller relative period of time to reach the predetermined mean particlesize.

[0133] The particular sonication test employed is not critical to thepresent invention and the selection of test and equipment is largelydetermined by practical considerations such as time allotted to performthe test.

[0134] For purposes of this specification, the “fragmentation potential”is defined as the percent increase in the percentage of particles whichare smaller than 40 microns after sonication for 30 minutes in theaqueous medium, plus a dispersant using an Horiba LA 900 instrument.Calculation of the fragmentation potential, of course, involves takingthe percent of particles which are smaller than 40 microns after 30minutes and subtracting the percent of particles smaller than 40 micronsin the sample before sonication. It was recognized that the initialsample could have some spheres of less than 40 microns agglomerated withsomewhat larger spheres. A preferred variation is to initiallydegglomerate the sample by sonicating the sample for one minute toobtain a base value for the percent of particles smaller than 40 micronsbefore sonicating for 30 minutes as described herein. In this instance,the fragmentation potential is calculated by taking the percent ofparticles smaller than 40 microns after 30 minutes and subtracting thepercent of particles smaller than 40 microns in the sample after aninitial one-minute sonication. The fragmentation potential using thepreferred technique is lower, as expected. In the data to be givenbelow, the fragmentation potential is given as (30-0) or (30-1), the “0”indicating no pre-sonication, and the “1” indicating a pre-sonication ofone minute. In an analogous test, the sonication number is determined asthe time for the mean particle size of a test sample to fall to 40microns.

[0135] Preferably, the fragmentation potential is from 10 to 84 percent,more preferably above 30 percent, and most preferably above 30 to 60percent.

[0136] Similarly, the Sonication Number is preferably from 5 to 200minutes, more preferably from 10 to 150 minutes, and most preferablyfrom 20 to 100 minutes. These numbers are obtained when using a MolvernParticle Size Analyzer with a 300 mm focal length and an active beamlength of 2 mm.

[0137] The fragmentation potential and sonication numbers set forthabove are for the silicas and mixed oxide silicas of this inventionafter calcining at 400° C. for 1 hour. The fragmentation potential andsonication number will, of course, vary depending on whether thecatalyst base is tested before or after calcining; before or after theaddition of chromia, etc. Likewise, the optimal fragmentation potentialwill differ from other bases such as silica.

[0138] While not wishing to be bound by any theory, it is believed thesonication technique is a unique tool for providing a fingerprint of animproved ethylene polymerization catalyst because of the shattering ofthe particles as shockwaves move through the internal pore structure.Accordingly, it is believed that such a process closely resembles thefracturing process which can occur during polymerization, i.e., thecatalyst particle breakup due to the accumulation of polymer andpressure within the pore structure.

[0139] (5) Microscopy

[0140] The new silica and mixed oxide silica compositions of thisinvention possess very unique and important characteristics over thesilicas and mixed oxide silicas of the prior art, i.e., the new silicasand mixed oxide silicas have a microstructure of encapsulated regionswith true macropores within a non-particulate, dense, continuous networkmatrix. And in one embodiment, they also exhibit sheet structures.

[0141] Physically, the new silicas and mixed oxide silicas are spraydried to form a non-particulate, dense, continuous network matrix withencapsulated regions of true macropores. The mean mesopore diameter isin a range of from 60 to 250 Å. The microscopic examination of theseregions is done using standard transmission electron microscope (TEM)techniques. For example, to observe the TEM specimen in the bright fieldimaging mode, it is necessary to prepare the TEM specimen by themicrotomy technique.

[0142] The microtomy technique is a well established specimenpreparation technique in the field of transmission electron microscopy.Its description can be found in standard reference published literature,for example, T. F. Malis and D. Steele, “Ultramicrotomy for MaterialsScience”, in “Workshop on specimen preparation for TEM of materials II”,ed. R. Anderson, vol. 199, Materials Research Symposium Proceedings(MRS<Pittsburgh, 1990) and N. Reid, “Ultramicrotomy”, in the “Practicalmethods in electron microscopy” series, (ed. A. M. Glauert, publ.Elsevier/North Holland, 1975). Briefly, it involves embedding the samplein a resin, form a pellet by polymerizing the resin in a mold, then cutthin sections using a microtome equipped with a diamond knife. In thework for this specification, the resin used was L.R. White resin. Thetypical thin section would have a thickness of about 0.06 microns. Careneeds to be taken to embed whole encapsulated regions in order thatviews of the entire random cross sections of the true macropores arepresented. Furthermore, it is important that prudent sampling techniquesbe used to collect the sample to be used for the TEM specimenpreparation step. The portion of encapsulated regions that were embeddedshould be selected from a sample by sequentially dividing the originallycollected sample into quarter portions until the desired amount ofmaterial suitable for the embedding process is reached.

[0143] In the TEM examination of specimens, it is always a balancebetween the amount of details to be observed and the amount of materialto be examined to ensure representativeness. To observe the increasingdetails of relevant microscopic features requires higher magnificationswhile this decreases the filed of view and the amount of materialexamined. However, a modern microscope allows the operator to easilychange magnifications from 100× to 1,000,000×. It is standard practiceto survey the sample at low magnifications, identify and confirm theviews that are typical and representative of the sample, then increasethe magnification as necessary to examine the details. Images will thenbe recorded to illustrate the characteristics of the sample. Therecorded images (which usually are on a 3.25″×4″ negative) are thenprinted and usually further magnified.

[0144] Such further magnification occurs by printing, for example, to an8.5×11″ print.

[0145] For the purposes of this specification, the images ofphotomicrographs have destination magnifications between 3000× and150,000×. The term “destination magnification” refers to the finalmagnification of the printed image.

EXAMPLES

[0146] The invention will be further illustrated by the followingexamples, which set forth particularly advantageous method embodiments.While the Examples are provided to illustrate the present invention,they are not intended to limit it.

[0147] The following are non-limiting examples of experiments involvingthe making and testing of both silicas and mixed silica oxides.

[0148] Tables 1 and 1A summarize the key process variables and theresulting physical properties of the formed and calcined SiO₂ powderresulting from the CHSG experiments. Examples 1 through 13 SiO₂ powderswere formed by vacuum drying the gel-cake, and crushing and sizing.Examples 14 through 17 were spray dried with the Stork Bowenspray-dryer.

[0149] Both sets of samples were calcined at 400° C. for one hour priorto characterization.

[0150] Tables 2 and 3 summarize the observations associated with each ofthe CHSG, continuous, high shear, experiments. TABLE 1 Summary of thePreparation Conditions for the SiO₂-bases of This Invention 8 Example No1 2 3 4 5 6 7 C1935- Notebook No C1935-23A C1935-23B C1935-23N C1935-31C1935-38A C1935-38A C1935-38B 38B(3) I) Solutions Na₂O:SiO₂,1:3.22,Kg0.6831 0.6831 0.6831 1.591 1.75 1.75 1.75 1.75 (Banco Sodium silicate 41Be 2.5 2.5 2.5 7 7 7 7 7 DI H₂O, Kg. 11.8 11.8 11.8 12.2 12.2 12.2 12.212.2 pH 3 to 1 3 to 1 3 to 1 6 to 1 6 to 1 6 to 1 6 to 1 6 to 1 w/w DIH₂O/H₂SO₄ 1.1 1.1 1.1 1.01 1.2 1.2 1.2 1.2 pH II) Gelation Statorconfiguration Slot Slot Slot Slot Screen Screen Screen Screen RPM ofRotor 7563 7563 7563 7723 7700 7700 7700 7700 Apparent Average Shear5.36 5.36 5.36 5.48 5.46 5.46 5.46 5.46 Rate x (10)⁴ pH Range 2 to 10 2to 10 2 to 10 5 to 7 5 to 7 5 to 7 5 to 7 5 to 7 Acid Rate gm/min 72 to220 72 to 220 72 to 220 100 67 67 67 67 Base Rate, gm/min 630 to 670 630to 670 630 to 670 548 351 351 351 351 pH at outlet — — — 7.5 9 9 9 9 GelT, C. 21 21 21 21 20 20 20 20 III) Washing Batch Yes Yes Yes Yes Yes YesYes Yes Wash Solution NH₄ Acetate NH₄ NH₄ Nitrate NH₄ Acetate NH₄Acetate NH₄ Acetate NH₄ NH₄ Bicarbonate Bicarbonate Bicarbonate pH ofWash Solution 7.3 8.4 5.3 7.3 7.3 7.3 8.4 8.4 Wash Temperature, C.Ambient Ambient Ambient 50 Ambient 50 Ambient 50 Conductivity of WaterWash (1) Initial,mmhos/cm² 8400 — 9250 8000 7000 10000 6800 7250 (2)Final 2300 1200 2600 2400 1950 2600 1350 500 Water Wash Temperature, C.Ambient Ambient Ambient 50 Ambient 50 Ambient 50 Diafiltration No No NoNo No No No No Dilution,Wt % Solids(LOM) Wash Solution pH of WashSolution Conductivity of Water Wash (1) Initial (2) Final Water WashTemperature, ° C. Wt % Solids of Concentrate IV) Aging pH Acid/BaseTime, Min Temperature V) Drying 80° C. in 80° C. in 80° C. in 80° C. in80° C. in 80° C. in 80° C. in 80° C. in Vacuum Vacuum Vacuum VacuumVacuum Vacuum Vacuum Vacuum VI) Physical Properties(2) SurfaceArea(BET),m²/gm 177 476 468 503 501 464 426 445 Pore Volume(BET) cc/gm0.521 0.939 0.924 1.004 0.929 0.998 0.949 0.985 MMPD,A 128 100 96 81 96115 117 119 Particle size, microns AASR = Apparent Average Shear Rate,reciprocal seconds (2) Measurement made after calcination for 1 hr at400° C.

[0151] TABLE 1A Summary of the Preparation Conditions for the SiO₂-Basesof This Invention Example No 9 10 11 12 13 14 15 16 17 Notebook NoC1935-43 C1935-42 C1936-50A C1936-50B C1936-50N C1935-44B C1935-44BC1935-47 C1935-48 I) Solutions Na₂O:SiO₂, 1.75 1.75 0.683 0.683 0.6834.098 4.098 4.098 1:3.22,Kg (Banco Sodium silicate 41 Be DI H₂O, Kg. 7 75 5 5 15 15 15 pH 12.2 11 11 11 11 11.2 11.2 11.2 w/w DI H₂O/ 6 to 1 6to 1 3 to 1 3 to 1 3 to 1 6 to 1 6 to 1 6 to 1 H₂SO₄ pH 1.2 <0 1.3 1.31.3 <0 <0 <0 II) Gelation Stator Screen Screen Screen Screen Screen SlotSlot Slot configuration RPM of Rotor 7700 7800 2729 2729 2729 10200 99239923 Apparent Average 5.46 5.53 1.93 1.93 1.93 7.23 7.04 7.04 Shear Ratex (10)⁴ pH Range 5 to 7 6.9 to 8.5 5 to 7 5 to 7 5 to 7 2.3 to 4.8 5.55.5 Acid Rate, 67 145 50 50 50 127 150 150 gm/min Base Rate, 351 692 680680 680 450 to 639 650 650 gm/min pH at outlet 9 7.3 — — — 6.5 4.1 4.1Gel T, ° C. 20 23 24 24 24 30 28 28 III) Washing No Yes No No Batch YesYes Yes Yes Yes Wash Solution NH₄ NH₄ NH₄ NH₄ NH₄ Nitrate NH₄Bicarbonate Bicarbonate Acetate Bicarbonate Bicarbonate pH of 8.4 8.47.3 8.4 5.3 7.9 Wash Solution Wash 50 50 Ambient Ambient Ambient 50Temperature, ° C. Conductivity of Water Wash (1) Initial, 7250 7250 — —— 6700 mmhos/cm² (2) Final 500 500 2300 1400 4000 1233 Water Wash 50 50Ambient Ambient Ambient 50 Temperature, ° C. Diafiltration No No No NoNo Yes Yes Yes Dilution,Wt % 2 3 3 Solids(LOM) Wash Solution NH₄ NH₄ NH₄Bicarbonate Bicarbonate Bicarbonate pH of 7.9 8 8 Wash SolutionConductivity of Water Wash (1) Initial 9360 — — (2) Final 300 2000 2000Water Wash 50 50 50 Temperature, ° C. Wt % Solids of 9 8.84 8.84Concentrate IV) Aging Yes No No Yes Yes pH 5.1 5.6 9.6 Acid/Base Aceticacid Acetic acid NH₄ Hydroxide Time, Min. 10 30 30 Temperature 38 50 50V) Drying 80° C. in 80° C. in 80° C. in 80° C. in 80° C. in Spray Dry80° C. in Spray Dry Spray Dry Vacuum Vacuum Vacuumn Vacuum Vacuum VacuumVI) Physical Properties(2) Surface Area 417 476 570 475 515 538 to 561378 471 to 487 454 to 474 (BET),m²/gm Pore Volume 1.128 0.844 0.8150.842 0.787 1.02 to 1.3 0.956 1.1 to 1.2 1.3 to 1.4 (BET) cc/gm MMPD, A162 79 67 82 71 101 to 140 114 140 to 167 151 to 167 Particle size, 6349 60 microns AASR = Appar- ent Average Shear Rate, reciprocal seconds(2) Measurement made after calcin- ation for hr at 400° C.

[0152] TABLE 2 Comparison of the Physical Properties and theMicrostructure of this Invention to Other Sources of SiO₂ Bases SiO₂-Commerical Commercial CHSG-Invention Source of SiO₂ Dispersion SiO₂ SiO₂1 2 5 14 16 17 Example Comparative Comparative Comparative C1935- C1935-C1935- C1935- C1935- C1935- Sample ID C1936-20-13 EP-30x EP-50 23A 23B38A 44B 47B 48B Surface Area(BET) 166 309 451 177 476 501 564 487 474Pore volume, PV,(N₂) 0.417 1.63 2.096 0.523 0.94 0.929 1.02 1.21 1.318Mean Meso Pore Diameter,A 113 206 183 128 100 96 101 140 151 GeometricPore Diameter,A 88 — 161 104 72 66 64 88 97 Pore Volume(N₂) > 100A0.2505 — 2.06 0.423 0.264 0.2199 0.2387 0.7187 0.88 Pore Volume(N₂) >200A 0.0082 — 0.395 0.0079 0.0319 0.04 0.0729 0.1554 0.188 PoreVolume(N₂) > 500A 0.0029 — 0.0157 0.0021 0.0083 0.0083 0.0133 0.02750.037 Fragmentation Potential — — 39 — — — 28 22 22 (30-1 min)“Apparent” Macro Yes Yes Yes — — — Yes Yes Yes PV(Hg) > 1000A MacroPV(Hg),cc/gm 0.529 0.15 0.492 — — — 0.215 0.38 0.44 “True” Macro PV(TEM)No No Yes Yes Yes Yes Yes Yes Microstructures(TEM) Particulates X XContinuous network X X X X X X X matrix Pockets (Lower density than X XX X X X matrix) Sheets X X

[0153] TABLE 3 TEM Characterization of SiO₂, Bases of the Prior Art andof this Invention Commercial SiO₂- Commercial SiO₂ CHSG-Invention Sourceof SiO₂ Dispersion SiO₂ Comparative 16 17 Example ComparativeComparative EP-50 1 2 5 14 C1935- C1935- Sample ID C1936-20-13 EP-30x(SiO₂/TiO₂) C1935-23A C1935-23B C1935-38A C1935-44B 47B 48 ParticulatesX X None None None None None None Size of 17 N.A. Particulates, nm Sizeof Pores 10 (estimated) Continuos X X X X X X X network matrix Densityof Matrix 3⁺ 1 3 2 2 4 Size of Matrix 20 8 7 10 10 25 Pores, nm PocketsX X X X X X Density of Pockets 5 1 2 2 2 Size of Pockets 1 2 3 3 3 Sizeof Pockets ˜15 Microns ˜10 Microns <10 Microns <10 Microns <10 MicronsPorosity of Pockets 3 1 3 2 2 Size of Pocket 70 85 20 30 80Pores,Typical,nm Size of Pocket 30 to 120 24 to 250 10 to 24 20 to 20025 to Pores,Range,nm 200 Sheets X X Quantity of sheets Only Onlyoccasionally occasionally observed observed Size of sheets About 0.02-About 0.1 0.15 microns microns thick and thick and 5- several 10 micronsmicrons length long

[0154] The General Procedure set forth above using the high shear mixerwas employed with specific amounts of reactants; shear rate, etc. as setforth in Tables 1 and 1A above. The characteristics of the silica aresummarized in Tables 1, 1A and 2.

[0155] Referring to Table 2, the silica possessed “true” macroporevolume as observed by TEM. It also possessed a continuous networkmatrix, with pockets of less density and occasional “unique” sheetmicrostructures.

[0156] Table 3 summarizes the characteristics of the matrix, pockets andsheets as observed by TEM.

Examples 1-2-3

[0157] Example 1 was split in thirds. Example 2 was washed initiallywith an ammonium bicarbonate solution as noted in Tables 1 and 1A.Example 3 was washed initially with an ammonium nitrate solution asnoted in Tables 1 and 1A. Both were then washed with DI water.

[0158] Referring to Tables 1 and 1A, Examples 2 and 3 had higher surfaceareas than Example 1; they had higher pore volumes; they had lower meanmeso pore diameters. This shows that washing affects the physicalproperties of the silica.

[0159] Referring to Table 2, Example 2 possessed “true” macropore volumeas observed by TEM. It also possessed a continuous network matrix withpockets of less density and occasional “unique” sheet microstructure.The “true” macropore volume of Example 2 was less than that of Example1.

[0160] Table 3 summarizes the characteristics of the matrix, pockets andthe sheets observed the TEM of Example 2. TEM showed that the density ofthe matrix of Example 2 was less than that of Example 1. However, thedensity of the pockets was higher. Example 2 had smaller pockets whichcontained smaller pores.

[0161] Chromium (III) acetate hydroxide was deposited onto the silica toresult in 0.7 weight percent chromium. The silica was first calcined at400° C. for 1 hour. The chromium compound was dissolved in methanol.

Example 4

[0162] Example 1 was repeated except for the differences noted in Tables1 and 1A.

Examples 5-8

[0163] Example 1 was repeated using a screen stator and the differencesnoted in Tables 1 and 1A. All the silica powders were high surface area,428 to 501 m²/gm. These examples illustrate the effects the washingsolution, washing conditions and degree of washing have on the physicalproperties.

[0164] Referring to Table 2, Example 5 possessed a continuous networkmatrix, pockets, but no sheets. It also possessed “true” macroporevolume.

[0165] Table 3 summarizes the characteristics of the matrix and thepockets observed in the TEM of Example 5. Example 5 had the least densematrix, compared to Examples 1 and 2. Example 5 had the most porouspockets with pores ranging from 24 to 250 nm (240 to 2500 Å).

Example 9

[0166] Example 5, 20 grams, was blended with 400 grams of DI water andacetic acid in a Waring Blender. The pH was about 5.1. The mixture wasblended for about 12 minutes. The final temperature was 38° C. The blendwas filtered. The gel-cake was vacuum dried at 80° C. overnight. It wasthen calcined at 400° C. for one hour and then ground and sized.Compared to Example 5, Example 9 had a lower surface area, 417 m²/gmversus 501 m²/gm. But Example 9 had both a larger pore volume, 1.128cc/gm versus 0.929 cc/gm, and a bigger MMPD, 182 Å versus 96 Å.

Example 10

[0167] Example 10 was essentially a repeat of Example 8 except for thedifferences noted in Tables 1 and 1A.

Examples 11-13

[0168] The General Procedure set forth above using the high shear mixerwas employed with the specific amounts of reactants; shear rate, etc.,as set forth in Tables 1 and 1A above. These silicas were prepared at alow AASR employing the screen stator.

[0169] Referring to Tables 1 and 1A, which summarizes silicacharacteristics, all these silicas were high surface area, greater than470 m²/gm.

[0170] Examples 14, 16 and 17 were washed by difiltration and formed byspray drying.

Example 14

[0171] The General Procedure set forth above using the high shear mixerwas employed with the specific amounts of reactants, shear rate, etc.,as set forth in Tables 1 and 1A above.

[0172] Referring to Tables 1 and 1A, this silica powder had highersurface area, more pore volume, and a larger MMPD than the previousexamples, illustrating the impact of washing by difiltration and formingby spray drying.

[0173] Referring to Table 2, the silica powder possessed macroporevolume as measured by mercury porosimetry, about 0.215 cc/gm. It alsopossessed “true” macropore volume as observed by TEM. It was comprisedof a continuous network matrix and pockets of less dense material. Thefragmentation potential of this powder was 28.

[0174] Table 3 summarizes the characteristics of the matrix and pocketsas observed by TEM.

[0175] Chromium (III) acetate hydroxide dissolved in methanol wasdeposited onto the silica powder to result in 1.0 weight percentchromium catalyst. Chromium (III) acetate hydroxide dissolved in DIwater also was deposited onto Example 14 to result in a second 1.0weight percent chromium catalyst.

Example 15

[0176] A portion of Example 14 was batch washed as set forth above inthe General Procedure, and formed after vacuum drying by grinding thegel-cake as set forth in Tables 1 and 1A above.

[0177] Referring to Tables 1 and 1A, this silica powder, compared toExample 14, had a lower surface area, 378 m²/gm versus ˜550 m²/gm, alower pore volume, 0.958 cc/gm versus about 1.2 cc/gm, and smaller MMPD.

Example 16

[0178] Example 14 was repeated using the differences noted in Tables 1and 1A above. Acetic acid was added to the gel and enough DI water toallow for mixing with a Marine impeller mixer. (The pH of the slurryadjusted to 5.6.) The mixture was heated to 50° C. over 15 minutes andheld at that temperature for about 15 minutes. The slurry was spraydried.

[0179] The characteristics of the silica powder are summarized in Tables1, 1A, and 2.

[0180] Referring to Table 2, Example 16, compared to Example 14, had alower surface area, 487 m²/gm compared to 564 m²/gm, but the pore volumewas larger, 1.21 cc/gm versus 1.02 cc/gm, and the MMPD was bigger, 140 Åversus 101 Å. The “apparent” macropore volume was also larger, 0.38cc/gm compared to 0.215 cc/gm. Example 16 had “true” macropore volume asobserved by TEM. This clearly illustrates the benefit of hot aging inacid conditions. The fragmentation potential of this powder was 22.

[0181] Table 3 summarizes the characteristics of the matrix and thepockets. The hot aging in acid pH changed the characteristics of thepockets. Compared to Example 14, Example 16, after aging as describedabove, had more porous pockets with larger typical pores, 300 Å versus200 Å, and a wider range of pores in the pockets, 200 Å to 2000 Å versus100 Å to 300 Å.

Example 17

[0182] Example 14 was repeated using the differences noted in Tables 1and 1A above. Ammonium hydroxide was added to the material of the geland enough DI water to allow for mixing with a marine impeller mixer.The pH was adjusted to about 9.6. The mixture was heated to 50° C. over15 minutes and held at 50° C. for 15 minutes. The slurry was spraydried.

[0183] The characteristics of the silica powder are summarized in Tables1, 1A, and 2.

[0184] Referring to Table 2, Example 17 compared to Example 14, had alower surface area, 474 m²/gm to 564 m²/gm, but the pore volume waslarger, 1.318 cc/gm versus 1.02 cc/gm, and the MMPD was bigger, 151 Åversus 101 Å. The “apparent” macropore volume was also larger, 0.44cc/gm versus 0.215 cc/gm. Example 17 had “true” macropore volume asobserved by TEM. This clearly illustrates the benefit of hot aging inbase conditions. The fragmentation potential of this powder was 22.

[0185] Table 3 summarizes the characteristics of the matrix and thepockets. The hot aging in base pH changed the characteristics of boththe matrix and the pockets. The density of the matrix decreased and thesize of the matrix pores increased to 250 Å compared to 100 Å forExample 14. Compared to Example 14, Example 17, after aging as describedabove, had more porous pockets with larger typical pores 800 Å versus200 Å, and a wider range of pores in the pockets, 250 to 2000 Å versus100 to 300 Å.

[0186] Chromium (III) acetate hydroxide dissolved in methanol wasdeposited onto Example 17 to result in 1.0 weight percent chromium.

[0187] Silicas of this invention, such as Examples 1, 2, 7 and 14, madevia gelation of sodium silicate (base side) by sulfuric acid under shearconditions contain the microstructures described above. This is incontrast to a commercial silica base used for ethylene polymerizationdescribed in Example 19 which contain neither the sheets nor theencapsulated, non particulate regions with true macropores.

[0188] This is also in contrast to experimental materials made fromcommercial dispersions and blends of those dispersions.

Comparative Example 18 Gelling Commercially Available SiO₂ Dispersions

[0189] Two dispersions and mixtures thereof were used, with the SiO₂ ineach dispersion having a different microstructure. They were (1) Nyacolcolloidal silica, 40 Wt. % SiO₂ (amorphous) with a spherical structure;and (2) Snowtex-UP, 20-21 Wt. % SiO₂ (amorphous) with a fiber structure.In order to achieve the gelling of each dispersion, it was necessary todetermine the acceptable concentrations of the reacting SiO₂s, the pH,the temperature, and the type of mixing to achieve gelation in areasonable time. This was accomplished by using a heated glass reactorfitted with a marine-impeller mixer or polytron mixer and a means togradually adjust the pH of the reaction. Because the dispersionscontained minimal amounts of residual salts, washing the resulting gelwas not necessary.

[0190] Comparative Table 4 summarizes the key process variables and theresulting microstructure of the formed and calcined SiO₂ powdersresulting from the experiments done with the commercial SiO₂dispersions. All the gel slurries were formed by spray drying with theYamato spray dryer, Model DL41 and the resulting powders were calcinedin a muffle furnace at 400° C. for one hour. The experimental SiO₂'s(comparative examples) made from commercially available dispersions areas follows:

[0191] (1) 1936-21-32, made from 100 Wt. % Snowtex (fibers);

[0192] (2) 1936-45, made from a 50/50 blend of Snowtex (fibers) andNyacol (spheres);

[0193] (3) 1936-20-13, made from 100 Wt. % Nyacol (spheres). COMPARATIVETABLE 4 Sample 1936-21-32 1936-45 1936-20-13 Gel pH 4.93 5.6 5.13 Temp.° C. 58 50 38 Gel time Overnight 6 min 39 min Mixer Polytron Marineimpellar Polytron Blend 100% 50% Snowtex/50% Nyacol 100% Nyacol SnowtexParticulate <100 Å >100 Å ˜170 Å size: MMPD, Å 144 78 113 Packing:Densely Densely packed with large Densely packed packed cracks in about⅓ of the with uniformly larger formed particles formed spheres

Comparative Example 19 Physical and Microstructural Characteristics ofthe Silicas of this Invention Compared to Commercially Available Silicasand Silicas made from Silica Sols

[0194] SiO₂ powders of Comparative Table 4 were characterized. Thecharacterization can be broken down into three categories: commercialSiO₂ (commercial dispersions and blends), and experimental SiO₂(commercial dispersions and blends), and experimental SiO₂ (silicasalt/CHSG). The commercial materials are EP 30x and EP-50. Theexperimental SiO₂'s (comparative examples) made from commerciallyavailable dispersions are as follows:

[0195] (1) 1936-21-32, made from 100 Wt. % Snowtex (fibers);

[0196] (2) 1936-45, made from a 50/50 blend of Snowtex (fibers) andNyacol (spheres);

[0197] (3) 1935-11, made from a 25/75 blend of Snowtex (fibers) andNyacol (spheres); and

[0198] (4) 1936-20-13, made from 100 Wt. % Nyacol (spheres).

[0199] The experimental SiO₂'s made by gelling sodium silicate with acidvia CHSG are 1, 2, 5, 14, 16 and 17. The TEM data for several of thesebases is summarized below.

[0200] The matrix of EP-30x was mostly made up of individual particlesof irregular shapes and sizes. There were some areas where the particlesappeared to be sintered together and resembled the appearance of thecontinuous network. These areas were only a small fraction of the totalvolume of the sample.

[0201] EP-50 was made up of a continuous porous network of amorphousSiO₂. The pores appear to be about 200 Å. This is consistent with thevalue obtained via BET, about 100 Å. EP-50 contains TiO₂. The TEManalysis suggests that the TiO₂ is present as a second phase in the formof fine particles of about 10 Å and less in size.

[0202] The SiO₂ bases made from the dispersions and spray dried via theYamato appeared as smooth rounded macroscopic particles of uniformdensity. The larger spray dried particles, 5-20 microns, are made up ofsmaller, densely packed individual particles.

[0203] The different microstructures of the starting dispersions affectthe size of the particulates present in the microstructure. In fact, itlooks like the ratio of the fibers to spheres affects size and thepacking of the particulates in the microstructure: the amount ofcracking in the spray dried particles increases with the amount offibers, Snowtex, present in the blend.

[0204] The spray-dried SiO₂'s made from CHSG exhibit differentmicrostructures from the preceding materials. They consist primarily ofa non-particulate, dense, continuous-network matrix and not individual,fundamental particles. The secondary structure is composed of pockets ofless density, non-particulate regions with true macropores. The size ofthese pockets, ranging from 2 μm to 15 μm, varies with the preparationconditions. The density of the non-particulate, dense,continuous-network matrix also varies with the preparation conditions.Examples 1, 2, 5 and 14 (V*SEP) have the microstructures describedabove.

[0205] However, Examples 1 and 2 display a “unique” sheet structurealso. They contain a few sheets which are 0.02 to 0.1 microns thick andabout 5-10 microns long.

Example 20 Physical Properties of the Dried/Calcined Powders made fromSodium Silicate under Mixing with Shear

[0206] The range of the key physical properties achieved with theabove-described methods of the present invention described in Examples1-17 were measured as:

[0207] (1) surface areas from 150 to 600 m²/gm;

[0208] (2) mean mesopore diameter (MMPD) from 60 to about 250 Å;

[0209] (3) varying modality of the pore size distribution frommono-modal to multi-modal;

[0210] (4) measured pore volume (N₂) from 0.5 to 1.5 cc/gm;

[0211] (5) macropore volumes (Hg) up to 0.5 cc/gm;

[0212] (6) median particle size from 7 to 63 microns; and

[0213] (7) fragmentation potential from about 20 to about 30.

Example 21 TEM Characterization of SiO₂ Bases

[0214] The microstructure of SiO₂ base samples was evaluated withrespect to:

[0215] (a) the presence of pockets of different densities in the matrix;

[0216] (b) the density of packing in the matrix; and

[0217] (c) the presence of sheet structures.

[0218] Specifically, the typical sizes of the pores in the pockets andin the matrix were estimated. An assessment of whether there were truemacropores was also made. As a comparison to the SiO₂ bases of thisinvention, experimental SiO₂ bases (e.g., 1936-20-13) made fromcommercially available dispersions and commercial SiO₂ bases (EP-30x andEP-50) were also examined.

[0219] The comparison results are summarized in Tables 2, 2A and 3. EM2829 (1936-20-13) (FIG. 3) clearly showed that the experimental SiO₂base made from silica dispersion was made up of particulates, while EM3309 (EP-50) (FIG. 4) showed that the matrix of EP-50 was made up of acontinuous network. For EP-30x, its matrix was made up of mostlyindividual particulates. However, the shape and size of theseparticulates were not as homogeneous as those in 1936-20-13. In someareas, the particulates appeared to be partially sintered and resembledthe continuous network. The matrices of all of the examples in thisinvention were made up of continuous networks. In addition, they allcontained pockets where the density of packing was lower than thesurrounding matrix. The number density of the pockets in the matrix(frequency of occurrence), the size of the pockets, and the porosity ofthe pockets were evaluated in a numerical relative ranking from 1 to 5.It should be noted that the ranking scale was neither linear norproportional. It only served to indicate an observable relativedifference. Furthermore, sheet structures were observed in the Examples1 and 2 samples 1935-23A and 1935-23B: A photomicrograph of Example 21935-23B, EM 3821, is included as FIG. 5. The true macropores weretypically located in the pockets. They can be recognized as empty spacesin the silica framework in the low magnification images.

[0220] The difference in the effects between aging in acid and aging inbase was clearly observed and illustrated by comparing Example 1935-44B(EM 3735) (FIG. 6), Example 1935-47B (EM 3728) (FIG. 7), and Example1935-48B (EM 3743) (FIG. 8). Aging in acid did not change themicrostructure of the matrix but increased the pore size in the pocketsslightly. Aging in base increased the pore sizes significantly in boththe matrix and the pockets.

Example 22 Batch Reactor Evaluation of Large Pore Silica Catalyst Bases

[0221] Three experimental catalysts were evaluated for their reactivity(activity compared to a Benchmark EP-30X 1.0% chromium catalyst) atconstant ethylene maximum consumption, temperature, reactor volume,heptane addition, agitation via stirring, ethylene pressure, andaluminum to chrome ratio. The catalysts were activated at either 600° C.or 800° C. as indicated in Table 5 below which summarizes the reactorresults. EP-30X, a commercial catalyst discussed above in Example 21,was the benchmark catalyst. The experimental catalysts 1935-48B (acatalyst of the present invention discussed above in Example 21),1935-44 (a catalyst of the present invention also discussed above inExample 21), 1934-44 (also a catalyst of the present invention) werecompared to it. The activity of the catalyst on a gram of polymer pergram of chromium varied with the catalyst.

[0222] The catalyst activations were performed on a bench-scale 28 mmdiameter fluidized bed under a stream of dry air at either 600° C. or800° C. for 8 hours. The activator tube is constructed from a 28 mmdiameter quartz frit, and a 67 mm diameter quartz disengaging section.The fluidization section is 300 mm long from the frit to the half angletransition, and the disengaging section is 400 mm tall. The transitionincorporates an 11° half angle for ideal transition in fluidized beddesign. The whole activator tube is enclosed in a Lindberg furnace andcan be purged with argon or low dew point air, typically ˜1L/minute. Gasflow direction is from the bottom to the top, and a cyclone trap isconnected to the outlet to collect fines, which might otherwise escapeinto the atmosphere. This scaled-down activation protocol mirrors thatused in the 4″ and 6″ activators at the Orange, Tex., pilot plant.′

[0223] Polymerizations were performed in 2L autoclave reactors equippedwith Genesis control systems. A dried 316ss 2L Autoclave EngineersZipperclave reactor system is heated at 80° C. in vacuo until a pressureof <50 mtorr is achieved. The reactor is then charged with a solution of0.2885 M 0.65 IBAO in 100 ml of heptane and a slurry of experimentalcatalyst in 100 ml heptane. The IBAO and catalyst amounts vary in μL andgrams respectively to give an Al to Cr proportion of 8.4 indicated inTable 5 below. The IBAO solution and Catalyst slurry were contained in a500 ml glass addition funnel that is fitted with a Kontes vacuum valve.The Kontes valve is connected to the reactor on a Cajon Ultra-Torrfitting, and the mixture is introduced into the reactor in-vacuo. Thereactor is stirred at 550 rpm and ethylene is introduced to an internalsetpoint pressure of 300 psi. The reactor temperature is maintained atthe setpoint temperature of 80° C. with a Neslab RTE-100 silicone orwater-bath circulator. The reactor is allowed to proceed to a givenproductivity, typically depletion of 80 L of ethylene, after which thereactor is vented and purged three times with argon and shut down. Thereactor is opened while it is still hot and the contents are quicklyremoved. The reactor is cleaned and prepared for the next reaction.¹

[0224]¹ The description of the activation technique and batch reactorsetup and conditions are similar to previous work completed by Ed Vegafor Pamela Auburn and Theresa Pecoraro in “Alpo Catalyst Batch ScreeningStudies”, April 1994 and are reprinted here with permission from PamelaAuburn.

[0225] Referring to Table 5, it can be seen that activity of theexperimental catalysts are superior to the commercial benchmark. TABLE 5Experimental Batch Reactor Runs for Large Pore Silicas Prior Weight IBAORun Run oxi- Activation % co-cat. Catalyst Al/Cr Polymer Time Liter C₂=Activity Activity Reactivity Sample ID number dation (degrees C) Crsoln. (μ l) (g) ratio Yield (g) (hr) consumed (g/g/hr) (g/mol/hr) EP30X8 III 800 1.0 590 0.150 5.9 109.16 1.15 80.10 632.8 26.5 1.0 EP30X 15III 800 1.0 590 0.150 5.9 114.03 1.07 80.10 710.5 29.8 1.1 C1935-48 16III 600 1.0 700 0.125 8.4 108.30 0.76 81.68 1140.0 39.1 1.8 MEOHC1934-44 22 III 600 1.0 700 0.125 8.4 95.17 0.67 80.64 1136.4 39.5 1.8MEOH C1935-44 H₂O 23 III 600 1.0 700 0.126 8.3 180.27 0.88 96.40 1625.847.6 2.6

Gelling Mixed Silica-oxide Salts

[0226] It is also possible to form gels from an acidic mixture of oxideprecursors and a sodium silicate plus acid by adding a base such asammonium hydroxide. In this case the acidic solution contained both asilica and an alumina precursor. The basic solution was ammoniumhydroxide. The acid and base solutions were mixed with high-shear,continuous gelation (CHSG) using a two-stream feed system pumpeddirectly into a Ross mixer (reactor) as described above. This resultingsilica-alumina contained a unique sheet-like structure.

Example 23 Procedure for Preparing SiAl of Prior Art

[0227] The following is a description of the procedure by which Example1252-36B, a conventional silica alumina, 60:40 wt ratio, was prepared.Some of the process steps described below were used to prepare thesilica-alumina samples of the present invention. The difference was thatthe materials of the present invention were prepared in the presence ofmixing with shear forces.

I—Starting Materials

[0228] Material Source Key Concentration Aluminum Chloride 32 BE Reheis10.8% Al₂O₃ Glacial Acetic Acid JT Baker 99.9% Sodium Silicate 41 BE VWR40% w/v Sodium Silicate Ammonium Acetate Solution Amresco Inc. 65%solution

II—Chelation

[0229] 1. Add 22.2 lb. of DI water to a 55-gallon tank and turn on themixer (Nettco Model NSP 050 mixer).

[0230] 2. Add 53.92 lb. of aluminum chloride solution to the DI water.

[0231] 3. Add 4.05 lb. of acetic acid to the aluminum chloride solutionand record the pH. It should be <0.

[0232] 4. In a separate tank make up a sodium silicate solution bymixing 23.34 lb. of sodium silicate with 126.4 lb. of DI water. Recordthe pH. it should be around 12.

[0233] 5. Pump the sodium silicate solution into the aluminum chloridesolution at approximately 5 lb./min. with a Masterflex magnetic drivevein pump. NOTE: If the silicate solution is added too quickly, it maycome out of solution. The resulting solution should be clear. Measureand record the pH. It should be around 2.8.

[0234] 6. Make up a solution of ammonium hydroxide which is 1 part NH₄OHand 3.205 parts DI water w/w. It will take approximately 90 lb. of theammonium hydroxide solution to do the titration. Make an excess ofammonium hydroxide. Record the pH.

[0235] 7. Begin the titration by pumping the ammonium hydroxide solutioninto the acid solution (from step 3) at 918 ml per minute. Titrate to apH of 8.0. The titration was done in a 100-gallon tank using a LightninModel XD-43 mixer running at about 1788 RPM.

[0236] The following titration table is typical: Time min. Base Addedlb. pH 0 0 2.8 7 9.2 3.06 19 23.1 3.42 35 42.7 3.92 56 64.8 4.9 66 75 672 81.6 8 80 89.1 8.03

[0237] 8. At the end of the titration, add ammonium hydroxide asnecessary to maintain a pH of 8.0 for 3 hours. It should take about 1.6lb. of base over 3 hours to keep the pH at 8.0. The pH will drift themost during the first hour. After 2 hours, the pH should be fairlystable.

[0238] 9. At the end of three hours, begin washing the gel-slurry.

III—Quenching: Not applicable IV—Washing: Difiltration

[0239] The gel-slurry was washed with an ammonium acetate solutionconsisting of 1.8 liters of 65% ammonium acetate solution inapproximately 55 gallons of DI water followed by a DI water wash. UsedNew Logic's V*SEP difiltration equipment.

[0240] On day one, the gel was washed with 256 liters of acetatesolution for one hour. The conductivity went from 51,300 mmhos to 29,000mmhos. The next day, the gel was washed with 398 liters of the acetatesolution over 2 hours. The conductivity decreased to 11,000 mmhos. At11,000 mmhos, the wash liquid was changed to DI water. The gel waswashed with 719 liters of DI water over 4.5 hours to a conductivity of958 mmhos. On day three, the wash continued using 183 liters of DI waterover 1 hour to decrease the conductivity to the target of 600 mmhos.

Acidification/Concentration

[0241] The gel-slurry was acidified in a 20-gallon tank with mixing byan air driven mixer with a marine impeller. Approximately half of theslurry was acidified to a pH of 5.6 with 96.3 grams of acetic acid. Theacid was added in two increments of 71.3 and 25 grams. The first acidaddition was dumped in all at once. The second addition was added slowlyuntil the pH reached 5.6.

[0242] The acidification process takes about 20-30 minutes. During thattime, the gel is being de-watered. Once a stable pH of 5.6 is reached,the dewatering goes on for another 5-10 minutes before the gel gets toothick to pump out of the mixing tank. The final concentration was 8.6%solids by LOM.

[0243] The other half of the gel-slurry was acidified the following dayto a pH of 5.6 with 106 grams of acetic acid. The acid was added inincrements of 35.5 g, 28.3 g and 42.2 g. The first two acid additionswere dumped in all at once. The last addition was added slowly until thepH reached 5.6.

[0244] Again, the gel-slurry was dewatered during the process to a finalconcentration of 8.6% solids by LOM.

V—Aging: None VI—Spray Drying

[0245] The slurry was spray dried separately with a Stork Bowen Model BE1235 Spray Dryer.

Calcination

[0246] The powder was calcined in air in a fixed fluidized bed reactor.The calcination is an automated process which follows the followingprogram:

Program

[0247] 15 minute ramp to 213° F. 1 hour hold.

[0248] 20 minute ramp to 482° F. 1 hour hold.

[0249] 20 minute ramp to 762° F. 1 hour hold.

[0250] 20 minute ramp to 1100° F. 2 hour hold.

[0251] Cool to room temperature.

[0252] Table 6 summarizes the key process variables and the resultingphysical properties of the formed and calcined silica alumina powdersresulting from the CHSG experiments. Example 23 represents the priorart. Examples 24 and 25 represent material of this invention, 1934-45and 1935-13AF. Tables 7 and 8 summarize the observations associated witheach of the CHSG, continuous, high shear, experiments.

Example 24 This Invention

[0253] The same starting materials were used as above.

[0254] 26.96 lbs of AlCl₃ solution was added to 14.4 lbs of DI water.The acetic acid, 918 grams, was added to the aluminum solution. The pHwas less than zero. 11.18 lbs of the sodium silicate was added to 63.2lbs of DI water with mixing. The silicate solution was pumped into thealuminum-acetic acid solution over a period of fifteen minutes withmixing. The pH was about 2.3. An ammonium hydroxide: DI water solutionwas prepared by a 1 3.205 w/w dilution. The pH was 11.6. The acid andthe base solutions were pumped into the Ross high-shear mixer-reactor.The specifics are summarized in Table 6. The gel from the reactor wascollected in a tank of DI water with mixing. Acetic acid was added tokeep the pH at 8.0. The pH was maintained at 8.0 for one hour beforewashing.

[0255] The remaining process steps were similar to Example 23. Table 6contains the specifics.

Example 25 This Invention

[0256] The same starting materials were used as above.

[0257] 26.96 lbs. of AlCl₃ solution was added to 16.69 lbs of DI water.The acetic acid, 918 grams, was added to the aluminum solution. The pHwas less than zero. 11.18 lbs of the sodium silicate was added to 63.2lbs of DI water with mixing. The silicate solution was pumped into thealuminum-acetic acid solution over a period of fifteen minutes withmixing. The pH was about 2.3. An ammonium hydroxide: DI water solutionwas prepared by a 1 to 3.205 w/w dilution. The acid and the basesolutions were pumped into the Ross high-shear mixer-reactor. Thespecifics are summarized in Table 6. The remaining process steps weresimilar to Example 23. Table 6 contains the specifics. TABLE 6Preparation Conditions for the Silica/Alumina Bases of this InventionPrior Art This Invention Example No Comparative: 23 24 25 Notebook No1252-36B 1934-45 1935-13AF I) Solutions A) Al solution 32 Be AlCl₃, Lb.53.92 26.96 26.96 Glacial Acetic Acid(99.9%),Lb 4.05 2.025 2.025 DIH₂O,Lb 22.2 14.1 16.7 pH <0 <0 <0 B) Si Solution Na₂O. SiO₂, 1:3.22,Lb23.34 11.18 11.18 (Banco Sodium silicate,41 Be) DI H₂O,Lb 126.4 63.263.2 pH 12 11.6 11.5 C) NH₄OH Solution NH₄OH: DI NH₄OH: DI NH₄OH: DI H₂O= 1:3.205 w/w H₂O = 1:3.205 w/w H₂O = 1:3.205 w/w II) Gelation: HighShear No Yes Yes Stator configuration Screen Screen RPM of Rotor 27852680 Apparent Average Shear 1.97 1.9 Rate(1),x (10)⁴ pH Range 5 to 9 7.7to 8.5 Acid Rate, gm/min 1947 to 2231 1468 to 2793 Base Rate, gm/min 883to 1016 420 to 690 pH at outlet 8.8 7.7 to 8.5 Gel T,C 26 28 III) QuenchNo Yes No IV) Washing Batch No No No Wash Solution pH of Wash SolutionWash Temperature, ° C. Conductivity of Water Wash (1) Initial,mmhos/cm²(2) Final Wash Temperature, ° C. Dilution ,Wt % Solids (LOM) WashSolution NH₄ Acetate NH₄ Acetate NH₄ Acetate pH of Wash Solution 7.3 7.3Conductivity of Water Wash (1) Initial 11000 9000 12000 (2) Final 600455 518 Wash Temperature, ° C. Ambient Ambient 50 Acidified, pH 5.6 5.65.62 Wt % Solids of Concentrate 8.6 5.4 1 to 7 V) Aging No No No VI)Drying Spray Drying Spray Drying Spray Drying VII) PhysicalProperties(2) Surface Area(BET),m²/gm 249 422 319 to 340 PoreVolume(BET) cc/gm 0.865 0.527 0.524 to 0.644 MMPD, Å 173 81 90 to 105Particle size, microns 94 30 9

Example 26 TEM Characterization of Silica/Alumina Samples

[0258] The microstructure of the silica/alumina bases was evaluated withrespect to:

[0259] (a) the presence of pockets of different densities in the matrix;

[0260] (b) the density of packing in the matrix; and

[0261] (c) the presence of sheet structures.

[0262] Specifically, the microstructures of the samples of thisinvention Examples 24 and 25 (for example, 1933-45 and 1934-13AF) werecompared to a sample prepared without shear Example 23 (1252-36B). Thetypical sizes of the pores in the pockets and in the matrix were alsoestimated. The results are summarized in Tables 7 and 8 below. Theyshowed that only the samples made by the CHSG method contained sheetstructures. These samples also have a much denser matrix framework. Thisis illustrated by comparing EM 0331 (1252-36B) (FIG. 9) and EM 2269(1934-45) (FIG. 10).

[0263] A Silica/Alumina catalyst base, Example 25 (C1935-13A) made byhigh shear continuous gelations was also analyzed.

[0264] The material contains the unique sheet structure discussed above.The material is amorphous with no evidence of any kind of phaseseparation.

[0265] Tables 7 and 8 below summarize and compare the physicalproperties and TEM characteristics of Silica/Alumina bases of thepresent invention to the prior art. TABLE 7 Comparison of the PhysicalProperties and the Microstructure of the Si/Al Bases of This Inventionto the Prior Art Prior Art This Invention Example Comparative: 23 24 25Sample Id 1252-36B 1934-45 1935-13AF Surface Area,m²/g(BET) 249 422 319Pore Volume(N₂) 0.865 0.527 0.524 Mean Meso Pore 173.4 81 90 DiameterXRD Amorphous Amorphous Amorphous “True” Macro PV(TEM) No Yes YesMicrostructures(TEM) Particulates No No No Continuous network X X Xmatrix Pockets X X X Sheets No X X

[0266] TABLE 8 TEM Characterization of Silica/Alumina Bases of the PriorArt and of this Invention Prior Art This Invention Sample ID 1252-36B1934-45 1935-13A Fines Example Comparative: 23 24 25 Amorphous Yes YesYes Particulates No No No Size of Particulates Size of Pores Continuosnetwork X X X matrix Density of Matrix — — — Size of Matrix Pores, 50 to100 5 5 nm Pockets No X X Density of Pockets 5 5 (relative ranking) Sizeof Pockets, 2 to 5 5 microns Porosity of Pockets 4 4 (relative ranking)Size of Pocket Pores, 30 70 Typical,nm Size of Pocket Pores, 10 to 60 30to 500 Range,nm Sheets No X X Size of sheets Thickness, nm 20 to 100 20to 100 Length, microns 1 to 3 1 to 3

[0267] While the present invention has been described with reference tospecific embodiments, this application is intended to cover thosevarious changes and substitutions that may be made by those skilled inthe art without departing from the spirit and scope of the appendedclaims.

What is claimed is:
 1. An amorphous SiO₂ or mixed oxide silica basecomposition comprising: (a) a non-particulate, dense, continuous networkmatrix; and (b) encapsulated, less dense, non particulate regions withtrue macropores.
 2. The composition of claim 1, wherein the gel matrixfurther comprises a sheetlike microstructure.
 3. The composition ofclaim 1, wherein the composition has surface areas in a range of from150 to 600 m²/gm.
 4. The composition of claim 1, wherein the compositionhas a mean mesopore diameter in a range of from 60 to about 250 Å. 5.The composition of claim 1, wherein the composition has a measured porevolume in a range of from about 0.5 to 1.5 cc/gm.
 6. The composition ofclaim 1, wherein the composition has a macropore volume of at most 0.5cc/gm.
 7. The composition of claim 1, wherein the composition is a mixedmetal silica oxide selected from the group consisting of silica alumina,silica titania, silica zirconia and silica vanadia.
 8. Powders producedfrom the composition of claim
 1. 9. The powders of claim 8, wherein thepowders are spray dried.
 10. The powders of claim 8, wherein the powdersare vacuum dried.
 11. The spray dried powders of claim 9, whereinfragmentation potentials are in a range of from about 20 about
 30. 12. Acatalyst comprising the composition of claim 1 impregnated with acatalytic amount of at least one transition metal-containing compound.13. The catalyst of claim 12, wherein the at least one transitionmetal-containing compound is a chromium compound.
 14. The catalyst ofclaim 12, wherein the at least one transition metal-containing compoundis present in an amount of 0.1 weight percent or greater based on thetotal catalyst weight.
 15. The catalyst of claim 14, wherein the atleast one transition metal-containing compound is present in an amountin the range of from about 0.1 weight percent to about 10 weightpercent.
 16. A polymerization process comprising contacting the catalystof claim 12 with at least one alpha-olefin under polymerizationconditions.
 17. A method for preparing a silica gel composition which isa precursor material for a silica powder material with a microstructurecomprising a non-particulate, dense, continuous, network matrix andencapsulated, less dense, non-particulate regions with true macropores,the method comprising: (a) forming a first aqueous solution comprisingsilica ions; (b) forming a second aqueous solution capable ofneutralizing said first aqueous solution; and (c) contacting said firstand second aqueous solutions in a mixer-reactor under mixing conditionswith shear forces to form the silica gel composition.
 18. The methodaccording to claim 17 further comprising aging the silica gelcomposition in acidic or basic conditions for up to one hour.
 19. Themethod of preparing the silica powder composition from the silica gelcomposition prepared by the method of claim 17, comprising the steps of:(a) washing the silica gel with solutions of ammonium acetate,bicarbonate or nitrate; (b) washing the silica gel composition indeionized water to further replace salts-contaminated water in thecomposition with fresh water; and (c) drying the washed composition toremove substantially all water.
 20. The method of claim 19, furthercomprising calcining the dried composition for up to 8 hours at amaximum temperature of 450° C.
 21. The method according to claim 17,wherein said first aqueous solution is an acidic solution comprisingsodium silicate and acid wherein the second aqueous solution has a pHabove
 8. 22. The method according to claim 17, wherein said secondaqueous solution is an ammonia based material selected from the groupconsisting of ammonium hydroxide; ammonium carbonate; ammoniumbicarbonate and urea.
 23. The method according to claim 17, wherein saidfirst aqueous solution is a basic solution of sodium silicate andwherein the second aqueous solution has a pH below
 6. 24. The methodaccording to claim 17, wherein said second aqueous solution is sulfuricacid.
 25. The method according to claim 17, wherein the apparent averageshear rate in said mixer-reactor is greater than about 0.5×10⁴ sec⁻¹.26. The method according to claim 17, wherein said neutralization stepis conducted in such a manner that the pH of the combined first aqueoussolution and the neutralizing medium is controlled in the range of about3.5 to about
 11. 27. The method of claim 17, wherein said catalyst isactivated by being heated to a temperature in the range of 300° C. to900° C. for from 2 to 16 hours.
 28. The method of claim 21 furthercomprising the steps of: (a) preparing an aqueous slurry of amorphoussilica gel by continuously feeding an acidic solution comprising sodiumsilicate and acid to an emulsifier mixer while simultaneously andcontinuously feeding to said mixer an alkaline solution; (b) operatingsaid mixer with sufficient shear so that the precipitated silicate hassheets of silica in its microstructure; (c) recovering said silica fromsaid aqueous slurry using a vibrating filtration membrane to a solidscontent from 8 to 20 wt. %, after washing; (d) drying the silica from(c); (e) calcining the silica from (d); (f) dispensing a chromiumcompound substantially uniformly onto said silica from (d) or (e) toform a catalyst having from 0.01 to 4 wt. % chromium; (g) drying saidcatalyst; and (h) activating said dry catalyst from (f) by heating to atemperature from 300° C. to 900° C. for from 2 to 16 hours.
 29. Anolefin polymerization catalyst prepared by the method of claim
 17. 30.An olefin polymerization catalyst prepared by the method of claim 28.31. A polymerization process according to claim 15 comprising contactingat least one mono-1-olefin having from 2 to 8 carbon atoms per moleculeunder polymerization reaction conditions in a polymerization reactionzone with a catalyst comprising an active catalytic component on asilica support comprising (a) a non-particulate, dense, gel matrix; and(b) encapsulated regions with true macropores.
 32. A process accordingto claim 31, wherein said catalytic component comprises a chromiumcomponent on the silica support.
 33. A process according to claim 31,wherein said at least one mono-1-olefin is selected from ethylene;propylene; butene-1; hexene-1 and octene-1.
 34. A process according toclaim 33, wherein said at least one mono-1-olefin comprises ethylene andfrom 0.5 to 2 mole percent of one additional mono-1-olefin is selectedfrom propylene; butene-1, hexene-1 and octene-1.
 35. A method forpreparing silica alumina powder material with a microstructurecomprising a non-particulate, dense continuous network matrix,encapsulated regions with true macropores, and sheets, the methodcomprising: (a) preparing an acid aqueous solution comprising aluminumand silicon ions; (b) preparing a basic aqueous solution comprisingammonium hydroxide; (c) mixing the acidic aqueous solution and the basicaqueous solution in a mixer with shear forces to obtain a gel slurrywith a microstructure comprising a non-particulate, dense, continuousnetwork matrix, encapsulated regions with true macropores and sheets;(d) maintaining the gel slurry at approximately pH 8.0 for up to onehour before washing the gel; (e) washing the gel slurry first withaqueous acetate solution, then with water to obtain a gel conductivitybelow 1,000 mmhos; (f) acidifying and concentrating the gel slurry byadding acid to the gel slurry to achieve a pH below 6.0 while graduallyremoving water from the gel slurry; and (g) drying and calcining the gelslurry to form the silica-alumina powder material.